1. Field of the Invention
The subject invention relates to fiber optics and range finders in a broad sense and, more specifically, to such range finders employing fiber optics or optical fibers.
2. Information Disclosure Statement
The following disclosure statement is made pursuant to the duty of disclosure imposed by law and formulated in 37 CFR 1.56(a). No representation is hereby made that information thus disclosed in fact constitutes prior art, inasmuch as 37 CFR 1.56(a) relies on a materiality concept which depends on uncertain and inevitably subjective elements of substantial likelihood and reasonableness and inasmuch as a growing attitude appears to require citation of material which might lead to a discovery of pertinent material though not necessarily being of itself pertinent. Also, the following comments contain conclusions and observations which have only been drawn or become apparent after conception of the subject invention or which contrast the subject invention or its merits against the background of developments which may be subsequent in time or priority.
Previous fiber optics range sensors have been sensitive to factors that can cause significant range errors, such as surface texture, tilt and reflectivity variations of the test object.
In this respect, U.S. Pat. No. 3,327,584, by C. D. Kissinger, issued June 27, 1976, for a Fiber Optic Proximity Probe, discloses a light level system. U.S. Pat. No. 4,249,076, by J. Bergstrom et al, issued Feb. 3, 1981, for an Optical Measuring Device Using Optical Fibers, tried to stabilize the drawback of light level systems. Similarly, U.S. Pat. No. 4,358,960, by J. H. Porter, issued Nov. 16, 1982, for a Differential Fiber Optic Proximity Sensor, proposed the use of a pair of output light guides arranged with their light receiving ends at different distances from the test object so that intensities of reflected light received and transmitted by such guides provide for a null indication at a predetermined distance from the test object and will vary differentially as a function of distance variation.